His fader was Judge on de Arizona State Superior Court for 10 years, den served as de Arizona Attorney Generaw for one two-year term from 1948-49 before being appointed to de Arizona State Supreme Court where he served as a Judge for four years from 1949–53. DeConcini received his bachewor's degree from de University of Arizona in 1959, and his LLB from de University of Arizona in 1963. He den worked as a wawyer for de Arizona Governor's staff from 1965-67. Dennis DeConcini rejoined de waw firm of DeConcini McDonawd Yetwin and Lacy, which he and his fader had co-founded in 1968, after weaving de Senate in 1995.[2][3]

DeConcini sponsored an amendment (de DeConcini Reservation) to de Panama Canaw Treaty of 1977 which awwows de United States "to take such steps as each [de U.S. or Panama] deems necessary, in accordance wif its constitutionaw processes, incwuding de use of miwitary force in de Repubwic of Panama, to reopen de Canaw or restore de operations of de Canaw, as de case may be."

DeConcini was widewy noted as a member of de Keating Five in a banking and powiticaw contribution edics investigation during de 1980s which grew out of de U.S. Savings and Loan Crisis. The Senate investigation invowved Charwes Keating and Lincown Savings/Continentaw Homes, de sixf wargest empwoyer in de state of Arizona at de time. The Senate Edics Committee wooked into de actions of five United States Senators in rewation to deir actions connected wif Charwes Keating and concwuded dat Senators DeConcini, McCain, Gwenn and Riegwe "broke no waws or Senate edics ruwes, but were aggressive in deir actions on behawf of Charwes Keating." DeConcini did not run for a fourf term.

In de 101st Congress, DeConcini served on de Senate Appropriations Committee, chairing de Subcommittee on Treasury, Postaw Service and Generaw Government. He awso served on de Subcommittees on Defense, Energy and Water Devewopment and Foreign Operations, and on de Senate Judiciary Committee, chairing de Subcommittee on Patents, Copyrights and Trademarks. He served on de Subcommittees on Antitrust, Monopowies and Business Rights, de Constitution and de Courts.[5]

DeConcini served on de board of directors of de Corrections Corporation of America (now known as CoreCivic) from 2008 to 2014.[12] Starting in 2010, some individuaws protested his membership on de board, saying his invowvement is "not suitabwe for a pubwic figure wike DeConcini." Awdough he cwaims he has not wobbied for harsher immigration waws and sentencing practices, he admits meetings wif de Arizona Department of Corrections Director Chuck Ryan and "pubwicwy speaking in favor of" for-profit prisons.[13][14][15]

It was awweged dat, in 1979, DeConcini had insider knowwedge about de proposed route of de Centraw Arizona Project and dat he used dis knowwedge to purchase wand dat he resowd six years water to de federaw government for a gain of awmost $1,000,000.[16][17]